Process for the manufacture of ammonium dialkyldithiophosphates

ABSTRACT

Production of noncaking ammonium dialkyldithiophosphates of the general formula: IN WHICH R1 and R2 represent identical or different alkyl radicals having from one to six carbon atoms. The phosphates are produced by mixing dialkyldithiophosphoric acids with an alcohol in a molar ratio of smaller than 1:0.25, introducing gaseous ammonia into the resulting mixture, filtering off precipitated salt, washing the salt and drying it.

United States Patent Roszinski et a].

[ 51 June 20, 1972 41 PROCESS FOR THE MANUFACTURE OF AMMONIUMDIALKYLDITHIOPHOSPHATES [72] Inventors: flilmar koszinski,Kendenich nearCologne; Heinz l-Iarnisch, Loevenich near Cologne,

both of Germany I [73] Assignee: Kn'npsack Aktlengesellschalt, Koln,Germany [22] Filed: March 21,1969

{2| 1 A t. No.: 809,408

301 Forelgn Appllcltlon Priority Dntn 7 April 5, 1968 Germany ..P I7 68l5l.$

[52] US. Cl, ..260/987, 260/963 [5|] lnt.Cl. C07l9/l6 [58] Field ofSearch ..260/987 [56] References emu UNITED STATES PATENTS 2,373,8114/1945 Cook et al ..260/987 'x Primary Examiner-Lewis Gotts AssistantExaminer-Anton H. Sutto Attorney-Connolly and Hutz [57] ABSTRACTProduction of noncaking ammonium dialkyldithiophosphates of the generalformula:

7 Claims, No Drawings PROCESS FOR THE MANUFACTURE OF AMMONIUMDIALKYLDITHIOPHOSPHATES The present invention relates to a process forthe manufacture of ammonium-dialkyldithiophosphates of the generalformula:

in which R, and R represent identical or different alkyl radicals havingfrom one to six carbon atoms therein.

it is known that dialkyldithiophosphoric acids can be produced 'byreaction of phosphorus pentasulfide with alcohols, and that the salts ofthese acidscan be obtained by neutralization. With reference to thevarious cations, it is known that various dialkyldithiophosphoric acidsalt-production methods have been described in literature. However, noneof these earlier processes can be used for the production of noncakingammonium salts of the above acids, from nonaqueous solutions.

All conditions which initially appear to be quite suggestive forreaction of dialkyldithiophosphoric acids with ammonia in an inertsolvent produce ammonium salts that are very pure, yet cake together tohard lumps, all this without the ammonium salts being hydroscopic orhaving a remarkably changed chemical nature. The poor stability tostorage of such hard material may jeopardize its further use, orconsiderably restrict the normally widespread chemical applicability ofdialkyldithiophosphoric acids, especially in those cases whichnecessitate shipment of the material.

The present invention now unexpectedly provides a process for themanufacture of noncaking ammonium dialkyldithiophosphates of the generalformula given hereinabove, which comprises mixing thedialkyldithiophosphoric acids with an alcohol in a molar ratio ofdialkyldithiophosphoric acid/alcohol of smaller'than 1:0.25, preferably1:03 to 1:05, introducing into the resulting mixture at maximum of 1.10mols, preferably 1.00 to 1.02 mols, gaseous ammonia, per moldialkyldithiophosphoric acid, filtering off precipitated salt, washingthe salt and drying it.

The alcohols suitable for use in the present process include aliphaticalcohols having from one to six carbon atoms, which can be used singlyor in combination, and preferably include those alcohols whichcorrespond to the R and/or R -alkyl radicals in thedialkyldithiophosphoric acids used.

After having been filtered and washed, the salt is dried at temperaturesbetween 15 and 110 C., preferably while using a stream of air with atemperature between 20 and 50C.

The mixture of dialkyldithiophosphoric acid and alcohol isadvantageously used in combination with an inert solvent includingaliphatic and/or aromatic hydrocarbons having from five to eight carbonatoms, or carbon tetrachloride. Cyclohexane, toluene or benzene may moreespecially be used to that effect. The solvent should be used inquantities such that the maximum ratio of solvent volume to volume ofthe dialkyldithiophosphoric acid/alcohol mixture is 5:1, preferablyabout 1:1.

As' can readily be seen under the microscope, the ammoniumdimethyldithiophosphate, for example, is precipitated in the presentprocess in the form of coarse crystals, which appear to have a hexagonalshape, rather than in the form of fine needles. X-ray investigation hasshown that the change of the crystalline form entrains no change of theinner crystalline structure. In order to change the crystalline fonn, itis necessary for the dialkyldithiophosphoric acid/alcohol mixture to bepresent in the above ratio at the onset of the precipitating step. Whileno crystal form change similar to that produced in ammoniumdimethyldithiophosphate occurs in the furtherammonium-dialkyldithiophosphates during precipitation, the fact remainsthat this ratio enables the production of noncakingammonium-dialkyldithiophosphates. The precipitation with the use of analcohol/dialkyldithiophosphoric acid-ratio greater than that indicatedabove or with the use of even pure alcohol, which fails to improve thequality of the resulting products, is an uneconomic procedure because ofrapidly increasing salt low.

It is equally imperative for the arnmonianeutralization of thedialkyldithiophosphoric acids to be carried out in" the absence of anyexcess ammonia as the-salts dissolve therein andare rendered glutinousonce ammonia and acid are used in a molar ratio of 1 .02.

The salts so precipitated, which are filtered and washed, should bedried under mild conditions so as to obviate even slight decompositionthereof, which again results in the formation of glutinous products. Thedrying step is best achieved using a stream of warm air. The workingexamples described hereinafter were carried out with the useof a vacuumsuction filter and warm air was suction-drawn through the washed filtercake.

The products obtained by the present process fail to cake together evenafter prolonged storage. They are nonhygroscopic and having a purityvery good for this class of compounds.

The following examples illustrate the invention.

EXAMPLE 1 1 M01 (158 grams) crude dimethyldithiophosphoric acid wasdiluted with milliliters toluene. l8 Grams methanol were added to theacid/toluene-mixture so--produced and 1 mol (17 grams) gaseous ammoniawas introduced thereinto within'4 hours, at 21C., with thoroughagitation and cooling. The resulting ammonium dimethyldithiophosphatewas separated from the solution having the impurities therein, by meansof a vacuum suction filter. The filter cake was washed using 100milliliters toluene. The white, coarsely crystalline salt so ob-tainedwas dried within 5 hours by suction-drawing air of 30 C. therethrough.The resulting product has a purity of 99 percent and was obtained in ayield of grams. The salt was stored for a period of more than 2 monthswithout caking together.

EXAMPLE 2 ing the impurities therein, by means of a vacuum suctionfilter.

The filter cake was washed using 50 milliliters carbon tetrachloride and50 milliliters cyclohexane. The while, coarsely crystalline salt soobtained was dried within 5 hours by suction-drawing air of 30 C.therethrough. The resulting product had a purity of 98.2 percent and wasobtained in a yield of 85.2 percent. The salt was stored for a period ofmore than 2 months without caking together.

EXAMPLE 3 1 M01 (186 grams) crude diethyldithiophosphoric acid wasdiluted with 150 milliliters toluene. 20 Grams ethanol were added to theacid/toluene-mixture so produced and 1 mol 17 grams) gaseous ammonia wasintroduced thereinto within 2 hours, at 21 C., with thorough agitationand cooling. The resulting ammonium diethyldithiophosphate was separatedfrom the solution having the impurities therein, by means of a vacuumsuction filter. The filter cake was washed using 100 milliliterstoluene. The white, crystalline salt so produced was dried within 4hours by suction-drawing air of 40 C. therethrough. The resultingproduct had a purity of 99.5 percent and was obtained in a yield of 188grams. The salt was stored for a period of more than 4 months withoutcaking together.

EXAMPLE 4 1 M01 (242 grams) crude di-sec.-butyldithiophosphoric acid wasdiluted with 150 milliliters toluene. 25 Grams secondary butanol wereadded to the acid/toluene-mixture so produced and 1 mol (17 grams)gaseous ammonia was introduced thereinto within 2 hours, at 21 C., withthorough agitation and cooling. The resulting ammoniumdi-sec.-butyldithiophosphate was separated from the solution having theimpurities therein, by means of a vacuum suction filter. The

filter cake was washed using 100 milliliters benzene. The white,crystalline salt so produced was dried within 3 hours by suction-drawingair of 40 C. thcrethrough. The resulting product had a purity of 99.1percent and was obtained in a yield of 248 grams. The salt was storedfor a period of more than 4 months without caking together.

We claim:

1. A process for the manufacture of ammonium dialkyldithiophosphates ofthe general formula in which R and R represent identical or differentalkyl radicals having from one to six carbon atoms, which comprisesmixing dialkyldithiophosphoric acids with an inert solventkyldithiophosphoric acids with the alcohol in a molar ratiobetween 1:0.3 and l :0.5.

3. The process of claim 1, which comprises introducing into the saidmixture between 1.00 and 1.02 mol ammonia, per moldialkyldithiophosphoric acid.

4. The process of claim 1, wherein the filtered and washed salt is driedat temperatures between 15 and 1 10 C.

5. The process of claim 4, wherein the washed salt is dried using astream of air with a temperature between 20 and 50C.

6. The process of claim 1, wherein the maximum ratio of solvent volumeto volume of the dialkyldithiophosphoric acid/alcohol-mixture is 5:1.

7. The process of claim 6, wherein the ratio of solvent volume to volumeof the dialkyldithiophosphoric acid/alcohol-mixture is about 1:1

t t 4' i i

2. The process of claim 1, which comprises mixing thedialkyldithiophosphoric acids with the alcohol in a molar ratio between1 : 0.3 and 1 : 0.5.
 3. The process of claim 1, which comprisesintroducing into the said mixture between 1.00 and 1.02 mol ammonia, permol dialkyldithiophosphoric acid.
 4. The process of claim 1, wherein thefiltered and washed salt is dried at temperatures between 15* and 110*C.
 5. The process of claim 4, wherein the washed salt is dried using astream of air with a temperature between 20* and 50*C.
 6. The process ofclaim 1, wherein the maximum ratio of solvent volume to volume of thedialkyldithiophosphoric acid/alcohol-mixture is 5:1.
 7. The process ofclaim 6, wherein the ratio of solvent volume to volume of thedialkyldithiophosphoric acid/alcohol-mixture is about 1:1.